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Theobroma cacao L. (Malvaceae sensu lato) is one of the most important agricultural tree crops in the tropics. However, little is known about whether T. cacao is controlled via top-down (herbivore) or bottom-up (resource limitation) processes in plantations and in natural forests. This question was investigated in this study by planting seedlings of T. cacao in plots of primary and secondary tropical wet forest in northeastern Costa Rica, with a simultaneous planting of the same variety of seedlings in an adjacent reconstructed plantation that had a thin overstory of high canopy shade trees. Leaf growth and leaf damage (herbivory) were measured in the cacao grown under the contrasting systems over a three-year period, with one to two censuses per year. Seedlings grown in plantations were observed to have significantly higher amounts of leaf damage than seedlings grown in secondary or primary forest. Nonetheless, plantation-grown cacao grew much faster, had more leaves, and had larger leaves than forest-grown individuals. Furthermore, plantation-grown cacao plants were the only ones to produce flowers and fruits, and they did so within three years. This study demonstrates that the growth and survival of T. cacao is likely controlled by resource limitation (bottom-up control) rather than herbivory (top-down control), and that individuals in high light plantations reach reproductive status even with high rates of herbivore pressure. These findings can inform the choice of efficient cocoa farming system and management strategies to be adopted by cacao farmers in Costa Rica and other cocoa producing countries. [ABSTRACT FROM AUTHOR]

Abstract: Many ecosystems are now dominated by introduced species, and because dominant species drive ecosystem properties, these changes lead to increased uncertainty in estimates of carbon storage and cycling. We examined aboveground biomass in forests dominated by the introduced tree Rhamnus cathartica (common buckthorn) relative to forests dominated by native species, and measured aboveground biomass increment over a three-year period (2005–2008). Three of the four lowest biomass levels occurred in R. cathartica-dominated forests, and biomass in these forest types was stored primarily in trees 10–20cm DBH. By contrast, forests dominated by native trees (including those with R. cathartica understories) had the six highest biomass levels, and biomass was stored primarily in trees >50cm DBH. On average, forests dominated by R. cathartica stored half as much aboveground biomass (14.6±3.3kg/m2) as forests dominated by native tree species (28.9±8.3kg/m2). R. cathartica-dominated forests also had half the aboveground biomass increment of native-dominated forests (0.28 vs. 0.60kg/m2/year). Although known anecdotally as a fast-growing species, R. cathartica growth rates declined with increasing size. Between 2005 and 2008, R. cathartica individuals <10cm DBH grew faster than native species; however, R. cathartica individuals >10cm DBH grew consistently slower than native species. Overall, our findings indicate that intrinsic size limitations on R. cathartica will lead to lower biomass stocks in forests where it acts as a canopy dominant relative to forests dominated by native tree species. [ABSTRACT FROM AUTHOR]

Abstract: The transmission and interception of light through the canopy is an important indicator of forest productivity in tropical forest ecosystems, and the amount of light that eventually reaches the forest floor is influenced by its interactions with leaves, branches, fruits, and flowers among many different canopy elements. While most studies of forest canopy light interception focus on leaf area index (LAI), very few studies have examined wood area index (WAI), which may account for a substantial component of light interception in tropical forests. The influence of lianas on the interception of light and their overall contribution to WAI is a potentially important factor, but it is generally overlooked because of its difficulty to assess. In this paper we evaluate the relative contribution that lianas have to the overall WAI and canopy openness as function of successional stage via a latitudinal comparison of sites across the Americas (Mexico, Costa Rica and Brazil). Our results suggest that lianas significantly increase WAI and decreases canopy openness. However, lianas were absent at all of our study sites where canopy openness exceeded 60%. Our data are the first to explicitly document the role of lianas in the estimation of WAI and, overall, they will contribute to better estimations of ecosystem level LAI in tropical environments, where there is a lack of data on WAI. [Copyright &y& Elsevier]

Abstract: Ecological invasions are a major driver of global environmental change. When invasions are frequent and prolonged, exotic species can become dominant and ultimately create novel ecosystem types. These ecosystems are now widespread globally. Recent evidence from Puerto Rico suggests that exotic-dominated forests can provide suitable regeneration sites for native species and promote native species abundance, but this pattern has been little explored elsewhere. We surveyed 46 sites in Hawai’i to determine whether native species occurred in the understories of exotic-dominated forests. Native trees smaller than 10cm in diameter were absent in 28 of the 46 sites and rare in the others. Natives were never the dominant understory species; in fact, they accounted for less than 10% of understory basal area at all but six sites, and less than 4% on average. Sites with native species in the understory tended to be on young lava substrate lacking human disturbance, and were mostly located close to intact, native-dominated forest stands. Even where we found some native species, however, most were survivors of past exotic encroachment into native forest, rather than products of active recolonization by native species. In contrast with successional trajectories in Puerto Rico, Hawaii''s exotic-dominated forests can emerge, via invasion, without human disturbance and native Hawaiian plants are largely unable to colonize them once they appear. We suggest that a wide diversity of growth strategies among the exotic species on Hawai’i may limit the opportunities for native plants to colonize exotic-dominated forests. [Copyright &y& Elsevier]

Abstract: Lianas affect many aspects of tropical forest dynamics and thus the study of their ecology is critical for a comprehensive understanding of tropical forest ecology. Recently, we initiated a complete census of all lianas ≥1cm diameter in the 50ha forest dynamics plot on Barro Colorado Island, Panama using the census protocol developed by Gerwing et al. [Gerwing, J.J., Schnitzer, S.A., Burnham, R.J., Bongers, F., Chave, J., DeWalt, S.J., Ewango, C.E.N., Foster, R., Kenfack, D., Martinez-Ramos, M., Parren, M., Parthasarathy, N., Perez-Salicrup, D.R., Putz, F.E., Thomas, D.W., 2006. A standard protocol for liana censuses. Biotropica 38, 256–261]. This protocol marked an important advance in the study of lianas by providing a standard methodology that can be used for liana censuses worldwide, thereby making accurate comparisons among studies possible. During the course of our census, however, we encountered a number of recurring situations that were critical for accurate and repeatable liana censuses, but were not covered in the protocol of Gerwing and colleagues. In this paper, we present a supplemental protocol that covers these additional situations. Our supplement, combined with the protocol developed by Gerwing et al., provides a more complete set of methods with provisions for situations commonly encountered in liana censuses. [Copyright &y& Elsevier]

Background: The aim of this study was to identify a sampling strategy with high probability for detecting oral colonization by Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eikenella corrodens, Tannerella forsythensis, Prevotella Intermedia, Prevotella nigrescens, and Treponema denticola before and following mechanical periodontal therapy. Methods: Samples were taken from the following intraoral sites in 35 patients with untreated chronic periodontitis before and 1.5, 3, and 6 months after non surgical periodontal therapy: supra- and subgingival plaque from the deepest pockets in each sextant; pooled supra- and subgingival plaque from another six randomly selected, less affected teeth; mucosal swab samples from the tongue, tonsils, throat, and buccal mucosa; and stimulated and unstimulated saliva. Microbial species were identified by polymerase chain reaction (PCR). Results: Of the sampling of all assessed sites, the highest probability for simultaneously detecting the tested pathogens was found in respect to the combination of supra- and subgingival plaque samples taken from the most affected tooth in each sextant in untreated patients (probability: 83% to 95% for the assessed bacteria). These results were consistently observed throughout the study period. Conclusions: For determining the intraoral carrier state of patients with periodontitis, a combined sample of supra and subgingival plaque taken from the deepest periodontal pocket in each sextant may yield the most reliable result. This sampling strategy may be used in routine microbial testing and clinical research. [ABSTRACT FROM AUTHOR]

The abundance of lianas (woody vines) and the detrimental impact that they have on tropical rain forest trees is widely recognized. Lianas are particularly abundant in disturbed areas of the forest, such as logging gaps, and pre-harvest liana cutting has been widely recommended throughout the tropics to reduce the impact of lianas during and following tree harvest. The effectiveness of forest-wide liana cutting, however, is currently unresolved, particularly for reducing liana abundance in logging gaps. Furthermore, our understanding of the dynamics and rate of liana colonization in gaps is limited. We tested: (1) the speed at which lianas recruit into logging gaps and their dynamics afterwards; and (2) whether pre-harvest liana cutting actually reduces the abundance of lianas in post-harvest logging gaps. To test hypothesis 1, we compared liana recruitment in new, 1 and 6-year-old logging gaps. For hypothesis 2, we compared liana abundance and tree infestation by lianas in 1-year-old logging gaps in which all lianas had been cut 9 months prior to tree felling vs. 1-year old logging gaps in which lianas were not cut. Lianas recruited heavily into logging gaps within 1 year, mostly by means of stem sprouts, and many of these new stems were apparently able to persist for longer than 6 years. Lianas were significantly more abundant in the root/bole zone of gaps than in the canopy zone, mostly due to the vigorous regeneration of stem sprouts. Canopy openness was highest in gaps one year after logging, possibly due to the smothering effect of the lianas on developing trees. Although liana abundance increased significantly over the 6-year gap chronosequence, direct liana infestation of trees remained the same. Pre-logging liana cutting, however, significantly reduced the number of lianas and also the number of liana-infested trees in logging gaps. Consequently, liana cutting appears to be an effective method to reduce the abundance of lianas and thus minimize their detrimental effects on regenerating trees in logging gaps. [Copyright &y& Elsevier]

Lianas can have a large impact on the diversity, structure, and dynamics of tropical forests, yet they remain essentially unknown even in some of the most intensely studied tropical forests, such as La Selva Biological Station in Costa Rica. We quantified the diversity, abundance, and mortality of lianas in primary and selectively logged forest at La Selva for over 3 years, from January 1999 until July 2002. We measured, identified, permanently marked, and mapped all lianas ≥1.3 m in length and 2 mm in diameter, whether climbing or free-standing, in nine, 24 m×36 m (864 m2) plots. There were no significant differences in density, diversity, or mortality between primary forest and areas that were selectively logged approximately 50 years prior to our study. We found a mean density of 1493 lianas ha−1 and a mean species richness of 23 species per 864 m2 plot. Annual mortality was 9.4% over all size-classes, but was the highest for the smallest individuals (<2 cm in diameter). Annual mortality for larger individuals (≥5 cm) was much lower over the 3.5-year period (3.2% per year) and the five most abundant species suffered no mortality in this size-class. In contrast to many lowland neotropical forests, where Bignoniaceae and Fabaceae are reported to be the dominant liana families, at La Selva we found that Sapindaceae was the most speciose family and Dilleniaceae the most abundant. Moutabea aculeata (Polygalaceae) was the most abundant species, constituting approximately 17% of the individuals and having the lowest mortality of all 60 species. The 10 most abundant species at La Selva accounted for more than 60% of all individuals. Compared to other lowland sites in the neotropics, including other wet forests, the abundance and diversity of lianas at La Selva are very low. [Copyright &y& Elsevier]